The present invention relates to the production of chlorosilanes and more particularly the present invention relates to processes for treating particles in a silicone reactor so as to make the particles usable for longer periods of time in a silicon reactor which is utilized for the production of chlorosilanes.
The present commercial method of manufacturing organosilanes is well-known and it is described in U.S. Pat. No. 2,380,995 Rochow. This patent discloses a direct reaction of an organohalide and more specifically methyl chloride with silicon particles with particles composed of silicon metal to produce organochlorosilanes. Intermixed with such particles of silicon matter that is intermixed with silicon particles there is intermixed particles of copper where copper in conjunction with silicon forms a reactive mass. In practice this reaction is generally carried out in one of three types of equipment: the stirred bed type of reactor as described in Sellers U.S. Pat. No. 2,449,821, the fluidized bed reactor described in Reed, et al U.S. Pat. No. 2,389,931 or a rotary kiln.
In the production of organochlorosilane by such a process the two basic products of the reaction are organotrichlorosilanes and diorganodichlorosilanes. Such compounds are utilized in the production of organopolysiloxane resins described in U.S. Pat. Nos. 2,258,218 to 2,258,222. Organopolysiloxane fluids described in U.S. Pat. Nos. 2,469,888 and 2,469,890 and the organopolysiloxane elastomers described in U.S. Pat. No. 2,448,756. The above patents are the early patents in the area. Since that time, there has been substantial innovations in the field and substantial patent literature has evolved on different types of compositions that can be produced from the basic organo chlorosilane. As pointed out previously, the basic products of such a reaction are organotrichlorosilane and diorganodichlorosilane. The diorganodichlorosilanes are preferred to be produced in high production since they can be utilized most widely, in particularly to produce linear polysiloxane fluids and polymers for the production of heat cured rubber elastomers and room temperature vulcanizable silicone rubber compositions elastomers of various types. Along with these organochlorosilanes there are produced minor amounts of other organochlorosilanes, however, these are not as important as the diorganodichlorosilanes. The amount of organotrichlorosilane is desired to be kept to a minimum in the chlorosilane production as discussed above. The only use of the organotrichlorosilane is to produce branch-chained fluids and certain resins. The excess of such organotrichlorosilane has to be converted to other types of organochlorosilanes before they can be utilized in silicone production. Accordingly, it is preferred in the production of organochlorosilanes by the direct process of Rochow that the weight ratio of triorganochlorosilane to diorganochlorosilane that the weight ratio of these two materials be about 0.1 during the production of chlorosilanes by the Rochow process and preferably not exceed the 0.35 level. However, it has been found in most manufacturing operations that what will happen is that the ratio will stay about the 0.15 level when the reactor is started up with new material and after a period raise to in excess of the 0.2 level. In the early times when this happened, the old silicon particles and the copper catalyst in the reactor would be removed and new particles would be inserted to the reactor and the reaction restarted. However, this was costly in terms of manufacturing cost.
Accordingly, there was always research being carried out as to determine how to more fully utilize the silicon particles in the reactor such that the weight ratio of organotrichlorosilanes to diorganochlorosilanes could be maintained at the desired level for a longer period of time resulting in the maximum utilization of the silicon particles to produce diorganodichlorosilanes. One of the breakthroughs in this area is for instance disclosed in U.S. Pat. No. 3,133,109 Dotson which is hereby incorporated by reference. Dotson disclosed that fuller use of the silicone particles could be carried out in that the amount of diorganodichlorosilane is maximized with respect to the organotrichlorosilane by passing used particles as they were utilized in the fluid bed reactor through an external fluid energy mill. As an alternative to the external fluid energy mill, Dotson also disclosed the passing of the used silicone particles that is particles that were recycled from the reactor through a plurality of sonic jets located at the base of the reactor wherein the silicon copper particles and organic chloride was passed through the jets at near sonic velocity to create a comminution of the particles or the breaking up of the silicon particles as a result of the particles striking each other or the walls of the reactor.
In one aspect of such construction, the jets have been designed so that they can face each other at the bottom of a fluid bed reactor and the particles, in accordance, with Dotson disclosure are made to strike each other in portions of the lower parts of the fluid bed reactor construction side so as to be comminuted or to be broken up into smaller particles. However, it was found by utilizing such a method that from the same amount of silicon particles, a larger amount of diorganodichlorosilane could be produced where the ratio of diorganodichlorosilane could be kept near the desired 0.15 or less than 0.35 value and more generally at the less than 0.35 value for a longer period of time. Utilizing the Dotson process 12 to 15% of the silicon that was introduced in the reactor was never utilized to produce an organochlorosilanes and removed as waste silicon from the process. Utilizing the Dotson process it was generally considered that said silicon was poisoned and was no longer capable of being utilized to produce diorganodichlorosilanes. Accordingly, it was highly unexpected that these fines or fine particles located in the fluid bed reactor of Dotson could be taken and treated so that they could be reutilized to produce diorganodichlorosilanes such that the ratio of organotrichlorosilanes did not exceed 0.35 for a longer period of time and such that the amounts of silicon metal lost as waste from the overall process would be reduced to less than 8%.
Accordingly, it is one object of the present invention to provide a process for treating the used silicon particles in a silicon reactor so that they may be activated to produce diorganodichlorosilanes.
It is another object of the present invention to provide a process for treating the used silicon particles in a silicon ractor for producing organochlorosilanes where the particles can be utilized for longer period of time to produce diorganodichlorosilanes with the weight ratio of organotrichlorosilanes and diorganodichlorosilanes will not exceed the 0.35 level for longer period of time that was possible prior to the present invention.
It is still another object of the present invention to provide a process for treating used silicon particles from a silicon fluidized bed reactor is that the overall loss of silicon as waste from the reactor process does not exceed 8%.
It is still another object of the present invention to provide a process for abraiding used silicon copper alloy particles from a fluid bed silicon reactor for the production of organochlorosilanes so as to remove the surface coating of such particles so that such particles can be reutilized in a reactor to produce organochlorosilanes.
These and other objects of the present invention are accomplished by means of the disclosure as set forth herein and below.